When to switch to reserve?

[Nava]

Here's a question from a new owner. I rode my '81 GS850GL until the fuel gauge was right on E, to figure out when it was appropriate to switch to reserve.

Well it went to E, and there was still gas sloshing around in the tank, so I decided that meant to switch to reserve at E, and not before. Then, the bike shuddered and sputtered to a stop within 100 yards. Once I walked it to a safe spot I noticed gas running down the left side of my bike. I felt around the petcock and carbs 1 and 2, but couldn't determine where the gas had come from, because it was everywhere.

At that point, the bike was ornery to start, and wouldn't idle long when it would. I also could not get the leak to spring with my eyes on it. A buddy came to fill me up, and it started and ran on both Full and Res settings without incident.

I have since fiddled with Res at different tank fills without incident. So, what happened at that intersection? Also, is there any harm leaving it gravity feeding on Res?

Any advice appreciated...I like this place.

[chef1366]

You either have junk floating around the float bowls or you need a new petcock.
I'd clean the carbs, check the tank for rust and debris and change the petcock.

[posplayr]

Here's a question from a new owner. I rode my '81 GS850GL until the fuel gauge was right on E, to figure out when it was appropriate to switch to reserve.

Well it went to E, and there was still gas sloshing around in the tank, so I decided that meant to switch to reserve at E, and not before. Then, the bike shuddered and sputtered to a stop within 100 yards. Once I walked it to a safe spot I noticed gas running down the left side of my bike. I felt around the petcock and carbs 1 and 2, but couldn't determine where the gas had come from, because it was everywhere.

At that point, the bike was ornery to start, and wouldn't idle long when it would. I also could not get the leak to spring with my eyes on it. A buddy came to fill me up, and it started and ran on both Full and Res settings without incident.

I have since fiddled with Res at different tank fills without incident. So, what happened at that intersection? Also, is there any harm leaving it gravity feeding on Res?

Any advice appreciated...I like this place.

I watch my Odometer ( I have a 5.X gallon tank and get about 35 mpg) to 120-130 miles is about where reserve hits)and then wait for the engine to sputter, surge a little then switch. On a trip this gives you the best idea on how much gas you have left before a fill-up is required.

[Steve]

Are you sure you turned it to REServe and not to PRIme?

The RUN position will have the lever pointing straight DOWN.

REServe will need to have the lever rotated clockwise, so it is pointing FORWARD.
(That's the whole lever, not any little arrow that might be cast into it.)

PRIme will have the lever rotated fully anti-clockwise, so the lever is pointing REARWARD.


When to change? If you have the lever pointing DOWN, in the normal, RUN position, just run until it feels like it's running out of gas (as it will be). Rotate the lever so it is pointing FORWARD, be ready for a surge in power when the gas hits the carbs, plan on stopping in the next 30 miles or so.

There is no harm in leaving the lever in the RES position, but if you run out of gas with it in that position, it's a long, HARD push to any gas station.

What you DON'T want to do is leave the lever in the PRIme position for any longer than necessary. In that position, gas will flow freely into the carbs. If the float needles are in good shape, you might get away with it, but if any of them leak, you will have a flood. In both, the RES and RUN positions, the flow is controlled by engine vacuum. When the engine stops, so does the gas.

.

[veedub]

Most older bikes don't have a gas gauge at all when the bike starts to spit and sputter you reach down and switch to reserve and find the next gas station. If you wanted to though you could run on reserve all the time and when you felt that spit sputter you would be truly out of gas but it should not cause leaks at any setting except maybe prime if your floats don't seal. Check gas lines Ts between carbs, and the petcock itself

[BassCliff]

Greetings and Salutations!!

Hi Mr. Nava,

For reference, have a look at this...

Where Do These Hoses Go?

The bike tells me when to switch to reserve. It acts like it's running out of gas (sputtering, losing power). That's when I switch. Depending on how I'm riding, this could be anywhere between 140-180 miles.

Now let me dump a TON if information on you and share some GS850G lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[JEEPRUSTY]

Well you could run a tank down to its reserve line by driving in stop and go traffic. You should be getting very poor mileage in that situation.

And also do it once in sustained high speed highway driving.

You can check the odometer in both cases and know when to draw the line.

Oh bring a friend when you do this as it is nice to have comany in case the bike dies and refuses to start when switched to reserve.

I once ran a bike from a tank that had a measured small amount of fuel to see what I would get a WOT. Went down from about 50 mpg to 22 ish.
Not overly accurate as it was about a 10 minute drive. Funny what you will do when you are bored.

[chuck hahn]

And remember that if you run it out of gas in the ON position without switching to reserve, the bowls are now empty. At this point you will need to switch it to PRIME to refill them. Let it sit about 30 seconds or so to reprime and start it in the prime position. Once it starts switch it over to RESERVE. If you dont reprime them youll crank your battery dead in short order and it will just spit and sputter as you described. And as Steve said, if your driving anb it starts sputtering just turn it forward and it will pick back up in a second or two.

[Nava]

Thanks for all the responses, fellas. I wasn't getting email notifications of your responses, so sorry it took long to get back to ya! I did find that one float was sticking, but it was in bowl 4. Mysterious.

Carbs still leaked between 1 and 2 when I reinstalled, but it idled without incident for awhile after I knocked on bowl 1 with a heavy wrench. Not satisfied, I took it apart once more to check all the brass pieces in those carbs. I didn't think to check the T-connectors! Nothing seemed amiss, but now she won't start unless the choke is on and the idle adjust is cranked way up. It sounds like death, vibrates a lot, and throttle kills it. I checked the exhaust pipes coming out of the engine block and found that 1 and 4 are ice cold, 2 and 3 are super hot! But, the new plugs are sparking, so I think I'm still having carb trouble. All the pilot screws on the outside engine side of the carbs are even with each other (measured their depth from the lip of the hole with the vernier tool, instead of counting revolutions because they all "bottom out" at different points), and I bench synced...so I don't know why it's only getting fuel to the center pistons.

Unsure of the maintenance background, here's what I've done...
-Replaced the spark plugs
-Replaced gaskets for valve cover, breather and crank cover
-Checked but did not replace valve shims..many were tight, one too loose.
-Checked but did not replace intake boots on airbox and engine side of carbs...they are very flexible and un-cracked.
-Replaced o-rings in the carbs from Robert's cycle o-rings site
-Cleaned the carbs by putting the small pieces in plastic egg cartons and filling the egg compartments with carb spray overnight. I did not dip the bodies, but sprayed through all the passages.
-Adjusted floats to spec
-Replaced air and oil filters
-Weather-stripped airbox
-Changed oil

The petcock: Many of you mentioned this. I believe a previous owner already replaced it, because mine does not have a "prime", only Full and Res.

The tank: It's rust free.

Currently: I got busy with work and ended up bringing the carb rack to a place known for their carb work. I should get them back tomorrow and will try and get things back together by the weekend to see if the carbs were the only problem.

[1_v8_merc]

If I'm leaning hard into a turn and I get a little Sputtering, it's time for Reserve!

[derwood]

I would switch to reserve periodically over the course of the season whether I needed to or not just to exercise my petcock,(?!) and to keep water and stuff from accumulating in the bottom of the tank......
L.S.S..... don't "never switch to reserve"

[850GT_Rider]

Carbs still leaked between 1 and 2 when I reinstalled, but it idled without incident for awhile after I knocked on bowl 1 with a heavy wrench.

Yeah, that's the way I always fix carbs too. But it gives credence to the theory there's crap in them there carbs.

Not satisfied, I took it apart once more to check all the brass pieces in those carbs. I didn't think to check the T-connectors! Nothing seemed amiss, but now she won't start unless the choke is on and the idle adjust is cranked way up. It sounds like death, vibrates a lot, and throttle kills it.

That's acting like an air leak someplace.

All the pilot screws on the outside engine side of the carbs are even with each other (measured their depth from the lip of the hole with the vernier tool, instead of counting revolutions because they all "bottom out" at different points), and I bench synced...so I don't know why it's only getting fuel to the center pistons.

Other than the tried and true starting point of 3-4 turns out from lightly seated, the ONLY way to set those is with a carb sychronizer (manometer)

Checked but did not replace valve shims..many were tight, one too loose.

Those need to be within specification. Uneven performance and/or valve damage may result if they're not!

[Clone]

I can pretty much rely on getting 300km out of a tank before needing reserve. So when I start getting to the point of 300 I find a gas station. If it sputters when I am getting close to 300 I switch it to reserve.

[Steve]

All the pilot screws on the outside engine side of the carbs are even with each other (measured their depth from the lip of the hole with the vernier tool, instead of counting revolutions because they all "bottom out" at different points), ...

Why on earth would you set them THAT way?

What if one screw has one thread less than the others?
What if one screw has a longer taper?
What if the 'tower' on one carb was a little bit higher?
What if ...?

The fuel that is trying to get past those adjustment screws does not care that the TOPS of the screws are all "even". What really matters is that the holes that allow the gas mixture through are all open the same amount. Please do yourself, your bike and us, a favor. Turn all those screws IN until they seat lightly, then back them out THREE FULL TURNS. That is 3 full, 360-degree turns, not 3 'flips' of the screwdriver.

Other than the tried and true starting point of 3-4 turns out from lightly seated, the ONLY way to set those is with a carb sychronizer (manometer)

Other than the fact that 4 turns is approaching the limits of adjustability for the mixture screws, you need to know that ...
YOU DO NOT ADJUST THOSE SCREWS WITH A CARB SYNCHRONIZER.

If you are going to use ANY kind of tool to set the mixture screws, it will be a Colortune, which is a clear sparkplug that allows you to see the flame.
The screws that are adjusted while using the carb synchronizer are the ones BETWEEN the carbs not ON the carbs.

-Checked but did not replace valve shims..many were tight, one too loose.

If you went to the trouble to check them and found them tight, why not change the shims and make them right?

Tight valves will run hot and make the bike very hard to start. The valves will tighten with accumulated miles, so they won't be getting any better.

We are trying to point you in the right direction. You seem to be facing in that direction, but refuse to move.
I don't know what else I can do to help you at this point.

.

[850GT_Rider]

Other than the fact that 4 turns is approaching the limits of adjustability for the mixture screws, you need to know that ...
YOU DO NOT ADJUST THOSE SCREWS WITH A CARB SYNCHRONIZER.

If you are going to use ANY kind of tool to set the mixture screws, it will be a Colortune, which is a clear sparkplug that allows you to see the flame.
The screws that are adjusted while using the carb synchronizer are the ones BETWEEN the carbs not ON the carbs.

Whoops - my bad! Consider me duly chastised. Sorry for the misinformation.